Method for determining height maps and interferometer system for the same purpose

Abstract

This provides a method for determining the height map of a sample surface, including edges. [Solution] The method includes the steps of acquiring a phase map of the sample surface by an interferometer system (101), acquiring a pre-height map (102), identifying a first region and a second region (103), selecting a position adjacent to an edge in the first region and a position adjacent to an edge in the second region (104), determining a pre-height difference (105), determining the zero-phase edge height of the edge (106), determining height correction (107), and determining a height map (108). Furthermore, it includes a computer-readable data storage medium containing a computer program to be executed on the processor of the interferometer system.

Description

[Technical Field]

[0001] The present invention relates to a method for determining a height map of a sample surface including edges. The present invention further relates to an interferometer system for determining a height map of a sample surface including edges. The present invention further relates to a computer-readable data storage medium which, when executed on the processor of the interferometer system according to the present invention, causes the interferometer system to perform the method according to the present invention. [Background technology]

[0002] In this art, it is known to determine the height map of a sample surface by relating the phase of reflected light to its height via the wavelength of light used. For example, a phase map of a sample surface can be obtained using an interferometer system, such as a white light interferometer system, where the phase is determined by allowing the light reflected from the sample surface to interfere with a reference light beam. An example of white light interferometry for determining a height map can be found in EP2314982 B1, where the zero-phase crossing method is used. Such a method can have an accuracy on the order of 1 nm on continuous surfaces, i.e., surfaces without edges. [Overview of the project] [Problems that the invention aims to solve]

[0003] If edges with edge heights exceeding the wavelength of light used to determine the phase map exist on the sample surface, the phase map is generally not very accurate. Because the phase map is invariant when shifted by multiples of 2π, the method used to determine the phase map may not be able to distinguish between edges with edge heights of, for example, one or two wavelengths. This reduces the accuracy of the height map based on the phase map.

[0004] A known solution for improving the accuracy of height maps of sample surfaces with edges is obtained by a phase-based method. The location of the edges can be determined by inspection of the sample surface. The surface can then be divided into two regions separated by the edges. The average height of the first region can then be subtracted from the average height of the second region to obtain an improved estimate of the edge height, thereby correcting the original height map.

[0005] However, as the requirements for measurement accuracy, particularly for height map measurement, increase, for example in quality control processes, there is a need to further improve the accuracy of determining edge height. Increased accuracy in determining edge height may be related to increased accuracy in determining the height map of the sample surface.

[0006] The present invention aims to provide a method for improving the accuracy of height maps of sample surfaces having edges.

[0007] The object of the present invention is achieved by a method for determining a height map of a sample surface including the edge according to claim 1. [Means for solving the problem]

[0008] The method involves obtaining a phase map of the sample surface by determining the phase of light reflected from the sample surface, where the light has a specific (assoiated) wavelength. The phase map can be obtained using an interference fringe image, i.e., the phase is determined by comparing the light reflected from the sample surface with a reference light. The specific wavelength of the light can be the central wavelength of light used by the interferometer, for example, the central wavelength of light used by a white light interferometer.

[0009] The phase map contains phase information for each position on the sample surface. For example, the phase may be determined for each pixel of the optical sensor used to determine the phase map. Thus, each pixel may correspond to a position on the sample surface. In other embodiments, the resolution of the phase map may be greater than or less than the resolution of the sensor used.

[0010] The method further includes obtaining a pre-height map of the sample surface. The pre-height map may be obtained based on a phase map using known methods, such as those disclosed in EP2314982 B1. However, the present invention is not limited to this possibility. The pre-height map may be obtained using different means. The pre-height of the pre-height map may also be corrected using the methods described above, in which case positions separated by edges are grouped, the average height of the groups is determined, and the height of the groups is corrected based on the average height before the pre-height map is used in the method of the present invention.

[0011] A pre-height map may allow for the identification of edges present on the sample surface. In some embodiments, edges may need to be identified independently of the pre-height map, for example, based on different measurements.

[0012] This method involves identifying a first region and a second region of the sample surface. The first and second regions of the sample surface are separated by an edge. For example, the edge may divide the sample surface into two separate regions, such that the edge forms a closed loop. These regions may be identified as the first and second regions. However, the first and second regions do not need to completely cover the sample surface. For example, the edge may extend from the side of the sample surface to the center of the sample surface. This allows for a smooth path from one side of the edge to the other. In this case as well, the first and second regions can be identified on the sample surface on both sides of the edge.

[0013] This method includes selecting a first position adjacent to an edge within a first region and a second position adjacent to an edge within a second region, where the first position is on the opposite side of the second position. In other words, the first position and the second position are separated by the edge, that is, the height difference between the first position and the second position can be entirely attributed to the presence of the edge. The first position and the second position may correspond to pixels of an optical sensor used to determine a height map, such as a phase map.

[0014] This method includes determining a pre - height difference between the first position and the second position based on a pre - height map. The pre - height difference, for example, ΔH h can be determined by obtaining the height associated with the first position from the pre - height map and subtracting the height associated with the second position from the pre - height map. According to the present invention, the pre - height difference thus obtained can be said to be an uncorrected height difference since the pre - height difference has not yet been corrected.

[0015] This method includes calculating a phase height difference between the first position and the second position based on a phase map and a specific wavelength. The phase height difference is a measure of the phase difference between the first position and the second position and is determined based on the magnitude of the phase difference between the two positions and the specific wavelength. However, the phase height difference is determined as a measure of distance. For example, the phase height difference ΔH φ is ΔH φ = Δφ λ / 4π where Δφ is the phase difference between the first position and the second position, for example, in radians, and λ is the specific wavelength.

[0016] This method further includes determining the zero - phase edge height of the edge by calculating the difference between the determined pre - height difference and the determined phase height difference. For example, the zero - phase edge height ΔH is ΔH=ΔH h - ΔH φ where ΔH hΔH is the pre-height difference between the first and second positions determined based on the pre-height map. φ This is the phase height difference. Preferably, the phase height difference and the prior height difference are determined in the same units so that no additional conversion is required.

[0017] This invention relies on the insight that, since the net phase difference is subtracted from the determined prior height difference, the zero-phase edge height should be equal to an integer multiple of half of a particular wavelength. In other words, the zero-phase edge height should be 0 mod(λ / 2). A deviation of the zero-phase edge height from a multiple of half of a particular wavelength indicates an inaccuracy in the prior height difference, and therefore in the heights of the first and second positions.

[0018] To leverage this insight, the method further includes determining height correction by determining the difference between the zero-phase edge height and an integer multiple of half of a particular wavelength. Preferably, the nearest integer multiple of half of a particular wavelength is used to determine the difference.

[0019] Then, the pre-height map is corrected by the height correction by correcting the relative height between the first and second regions in the pre-height map based on the height correction. For example, the height of the first region is corrected by the height correction. In another example, the heights of both the second and first regions are corrected by half of the height correction. In embodiments, multiple height corrections for multiple positions along an edge may be determined according to the present invention. The final correction of the pre-height map may then be based on the multiple height corrections. This can improve accuracy, for example, when the edge height is not constant.

[0020] This invention makes it possible to improve the accuracy of height maps even when the edge height of an edge is greater than a specific wavelength.

[0021] In this embodiment, the phase map is a lap phase map. The lap phase map has phase values ​​constrained to lie within a principal interval, for example, a selected interval of length 2π. Phase values ​​outside the principal interval can be shifted by a multiple of 2π until the phase value lies within the principal interval.

[0022] In the embodiment, an interferometer system is used, for example, a white light interferometer system, and in this method, a pre-height map is acquired using the interferometer system, and a phase map is acquired using the interferometer system. For example, the pre-height map may be determined based on a known method, for example, a method disclosed in EP2314982 B1.

[0023] In this embodiment, the step of identifying the first region and the second region includes: A step of obtaining an intensity map of the sample surface based on the intensity of light reflected from the sample surface, Optionally, a step to remove the background from the intensity map, The steps include identifying an edge based on the fact that the intensity of a pixel in the intensity map differs from the intensity of surrounding pixels, for example, based on the fact that the intensity of a pixel falls below a predetermined threshold, A step of identifying the first region and the second region on both sides of the edge.

[0024] Generally, the edges of a sample surface reflect light in different directions compared to the surrounding areas, for example, because the local inclination angle of the edge differs from that of the surrounding area. Therefore, the position of an edge can be determined based on the intensity map of the sample surface.

[0025] In the embodiment, the pre-height map is obtained based on the phase map and a specific wavelength.

[0026] In the embodiment, the step of obtaining a phase map includes the following: A step of acquiring a group of interference fringe images by vertical scanning the sample surface through the focal plane of an interferometer system having an optical sensor, wherein each interference fringe image includes the measured light intensity for each pixel of the interferometer system at each height of the sample surface relative to the focal plane, The steps include determining the covariance matrix for the interference fringe image set, The steps include determining the principal components of the interference fringe image set by performing singular value decomposition of the covariance matrix, The steps include selecting a first principal component associated with the largest eigenvalue of the covariance matrix and a second principal component associated with the second largest eigenvalue of the covariance matrix, A step of determining the measured phase for each pixel of a plurality of pixels, for example, by taking the arctangent of the ratio of the vector component of the first principal component to the vector component of the second principal component, and each vector component is associated with each pixel. A step of determining a phase map based on the phase measured for each pixel.

[0027] In these embodiments, each interference fringe image in the interference fringe image set is associated with the height of the sample surface relative to the optical sensor and / or optical plane. To obtain the interference fringe image set, the sample surface is moved vertically, for example by vertical scanning, where the vertical direction is understood to be the direction parallel to the measured light beam on the sample surface. The sample surface may be moved between different measurement positions, and an interference fringe image is determined at each measurement position. The interference fringe image may be represented by an M×N matrix, for example, when the optical sensor has M×N pixels, where each entry in the M×N matrix contains the intensity of the associated pixel. The intensity contains information about the relative phase of the light measured at that pixel with respect to the associated interference fringe image. Thus, by obtaining Z interference fringe image sets, a total of Z M×N matrices can be obtained. For example, Z M×N matrices can be represented by a single 3D M×N×Z matrix. The 3D M×N×Z matrix representing the interference fringe image set is a 2D M*N×Z matrix A M*N×Z It can be transformed into a 2D M*N×Z matrix A, where each column is associated with an interference fringe image of the interference fringe image set.M*N×Z can be written as a sum. A M*N×Z = a Z u M*N + b Z v M*N Here, u M*N = B cos(φ M*N ) and v M*N = B sin(φ M*N ) where φ M*N is the measured phase related to the height of the surface at the pixel. B is the modulation amplitude, and a Z and b Z depend on the random phase shift and φ M*N does not depend on it.

[0028] The two signals u M*N and v M*N are approximately uncorrelated so that A M*N×Z can be decomposed into u M*N and v M*N , and thus it can be shown that the dependence on the random phase shift related to the random vibration of the sample with respect to the interferometer is removed.

[0029] The signals u M*N and v M*N can be obtained by performing principal component analysis on the interferogram image group, for example, on the matrix representing the interferogram image group A M*N×Z . For this purpose, the method further includes determining the covariance matrix for the interferogram image group. The covariance matrix can be a square and symmetric matrix that can be obtained by multiplying the matrix by its own transpose. The transformed two-dimensional matrix A M*N×Z can be multiplied by its transpose so that the M*N×M*N covariance matrix of the interferogram image group is obtained.

[0030] To determine the principal components of the interferogram image group, singular value decomposition can be performed on the associated covariance matrix. Singular value decomposition makes it possible to decompose a square matrix into an orthogonal matrix and a diagonal matrix. The principal components of the covariance matrix are then the matrix A M*N×ZThis can be obtained by calculating the projection. Y=ΦA M*N×Z Here, Y is A M*N×Z It includes the principal components of the interference fringe images, and Φ is the orthogonal matrix of the singular value decomposition.

[0031] The principal component associated with the largest eigenvalue and the principal component associated with the second largest eigenvalue are the signal u M*N and v M*N (These can be shown to correspond to vectors with each entry associated with a pixel of the optical sensor, and are proportional to the sine and cosine of the measured phase.) Therefore, u M*N and v M*N By taking the ratio of the components, the ratio of the sine and cosine can be determined. As a result, taking the tangent of such a ratio, for example, can lead to obtaining the measured phase at each pixel.

[0032] Therefore, this embodiment includes selecting a first principal component associated with the largest eigenvalue of the covariance matrix and a second principal component associated with the second largest eigenvalue of the covariance matrix, and taking the ratio of the ratio of the vector components of the first principal component and the second principal component. The measured phase can be determined based on this ratio. The height map is obtained based on the phase measured for each pixel, for example, based on the average wavelength of a broadband light source.

[0033] Using this embodiment, it can be shown that the measured phase obtained for a pixel may have an undetermined global sign. This global sign is a result of the use of the orthogonal matrix Φ in the singular value decomposition of the covariance matrix and the determination of the principal components. As can be understood, the orthogonal matrix Φ appears twice in the singular value decomposition of the covariance matrix and is therefore not uniquely determined due to the possible changes in its global sign. As a result, the global sign of the measured phase is unknown, since the determined principal components are also not unique, even down to their signs. The correct global sign can be determined by examining the phases of the first and second principal components. The first and second principal components, as seen as vectors, always have a phase difference of ±π / 2, which has the correct global sign of the height map, when the first principal component lags the second principal component by π / 2. If this is not the case, the global sign must be inverted with respect to the sign used when determining the Hilbert-transformed eigenvectors in order to obtain the correct height map.

[0034] To determine whether the measured global sign of the phase is correct, this embodiment may further include performing a Hilbert transform on the eigenvector of the covariance matrix associated with the largest eigenvalue of the covariance matrix to obtain a complex Hilbert transformed eigenvector. The real part of the Hilbert transformed eigenvector lags the imaginary part of the Hilbert transferred eigenvector by exactly π / 2.

[0035] Therefore, each vector component is associated with a reference pixel by determining the reference phase of the reference pixel of a pixel based on the ratio of the real and imaginary vector components of the Hilbert-transformed eigenvector, for example by taking its arctangent, and determining whether the measured phase of the reference pixel corresponds to the reference phase of the reference pixel. By checking whether the measured phase of the reference pixel corresponds to the reference phase, and if the measured phase does not correspond to the reference phase, it is possible to check whether the global sign of the measured phase is correct by, for example, inverting the global sign of the measured phase in the height map. Thus, this makes it possible to determine a height map of the sample surface with the correct global sign.

[0036] The correct global code may also be determined by the following procedure: The steps are: perform the Fourier transform of the first eigenvector of the covariance matrix associated with the largest eigenvalue, and then perform the Fourier transform of the second eigenvector of the covariance matrix associated with the second largest eigenvalue; The steps include determining the highest amplitude frequency of the Fourier-transformed first eigenvector, The steps include calculating the first Fourier phase of the Fourier-transformed first eigenvector and the second Fourier phase of the Fourier-transformed second eigenvector associated with the determined highest amplitude frequency, The steps include determining the difference between the first Fourier phase and the second Fourier phase by subtracting the second Fourier phase from the first Fourier phase, If the difference between the first Fourier phase and the second Fourier phase is between 0 and π modulo 2π, then the global sign of the determined height map is reversed.

[0037] Therefore, the phase difference between the first and second principal components is checked by examining the phase difference of the associated Fourier-transformed vectors. The global sign of the height map is inverted with respect to the sign used to check the difference between Fourier phases if the difference between the Fourier phases is between 0 and π modulo 2π.

[0038] The present invention further relates to an interferometer system for determining a height map of a sample surface including edges, the interferometer system comprising a light source, an optical sensor, and a processor, the processor configured to perform the following steps: A step of obtaining a phase map of the sample surface based on the measurement of light of a specific wavelength reflected from the sample surface using an optical sensor, A step of obtaining a pre-height map of the sample surface based on the measurement of light reflected from the sample surface by an optical sensor, A step of identifying a first region and a second region of the sample surface, wherein the first region and the second region are separated by an edge, A step of selecting a first position adjacent to an edge in a first region and a second position adjacent to an edge in a second region, wherein the first position is on the opposite side of the second position. The steps include determining the prior height difference between a first position and a second position based on a prior height map, and calculating the phase height difference between the first position and the second position based on a phase map and a specific wavelength, The steps include determining the zero-phase edge height of an edge by calculating the difference between the pre-height difference and the phase height difference, The height correction is determined by determining the difference between the zero-phase edge height and an integer multiple of half of a specific wavelength, A step of determining a height map by correcting the heights of the first and second regions in the pre-defined height map through height correction.

[0039] In this embodiment, the processor uses the following to achieve a phase height difference ΔH φ Configured to determine: ΔH φ =Δφλ / 4π Here, Δφ is the phase difference between the first position and the second position, and λ is a specific wavelength.

[0040] In this embodiment, the phase map is a wrap-around phase map.

[0041] In the embodiment, the interferometer system is a white light interferometer system equipped with a broadband light source, and the pre-height map is acquired using the white light interferometer.

[0042] In this embodiment, the processor is configured to identify the first and second regions by performing the following steps: A step of obtaining an intensity map of the sample surface based on the intensity of light reflected from the sample surface, Optionally, a step to remove the background from the intensity map, Steps include identifying edges based on the intensity of pixels in the intensity map that fall below a predetermined threshold, A step of identifying the first region and the second region on both sides of the edge.

[0043] In the embodiment, the processor is configured to determine a pre-height map based on a phase map and associated wavelengths.

[0044] In this embodiment, the processor is configured to acquire a phase map by performing the following steps: A step of acquiring a group of interference fringe images by, for example, moving the optical sensor relative to the sample surface, thereby scanning the sample surface perpendicularly through the focal plane of the optical sensor, wherein each interference fringe image includes the measured light intensity for each pixel of the interferometer system at each height of the sample surface relative to the focal plane. The steps include determining the covariance matrix for the interference fringe image set, The steps include determining the principal components of the interference fringe image set by performing singular value decomposition of the covariance matrix, The steps include selecting a first principal component associated with the largest eigenvalue of the covariance matrix and a second principal component associated with the second largest eigenvalue of the covariance matrix, A step of determining the measured phase for each pixel of a plurality of pixels, wherein the measured phase is determined based on the ratio of the vector component of the first principal component to the vector component of the second principal component, for example, by taking the arctangent thereof, and each vector component is associated with each pixel, A step of determining a phase map based on the phase measured for each pixel.

[0045] The present invention further relates to a computer-readable data storage medium which, when executed on the processor of the interferometer system according to the present invention, causes the interferometer system to perform the method according to the present invention. [Brief explanation of the drawing]

[0046] Herein, embodiments of the present invention will be described with reference, for example, to the accompanying drawings in which corresponding reference numerals indicate corresponding parts. [Figure 1] Figure 1 shows a white light interferometer used to determine the height map. [Figure 2] Figure 2 is a flowchart showing the method for determining the height map of the sample surface. [Figure 3] Figure 3 shows the sample surface with an edge. [Modes for carrying out the invention]

[0047] Figure 1 shows an example of a white light interferometer 1 for determining a pre-height map and / or phase map. The interferometer includes a broadband light source 2. Light 3 from the light source 2 can pass through lens 4a, a beam splitter 4b, and a second lens 4c. After passing through the second lens 4c, the light 3 is split by the beam splitter 5 into a first partial light beam 4a and a second partial light beam 3b. The first partial light beam 3a is directed to the sample surface 6 of the sample 7. The second partial light beam 3b is directed to a reference mirror 8 having a reference surface 9. After reflection by mirrors 6 and d8, the partial light beams 3a and 3b are combined and propagated to an optical sensor 10 having multiple pixels. For example, the optical sensor 10 may be a CCD array camera 10. This setup results in an interference signal on the optical sensor 10.

[0048] The pixels of the optical sensor 10 may correspond to positions on the sample surface 6 and the reference surface 9. After vertical scanning, each pixel may have an associated intensity signal that can be associated, for example, via phase, with the height at the corresponding spatial position of the sample 7.

[0049] The sample 7 can move through the focal plane of the second lens 4c, and interference fringe images are acquired by the optical sensor 10 for multiple positions of the sample 7 relative to the interferometer 1. In this way, the interferometer 1 can acquire a set of interference fringe images (101), which can be received by the processor 11, enabling the processor to determine a height map based on the method of the present invention.

[0050] Figure 2 shows a flowchart of a method for determining the height map of the sample surface 6. The method includes the step (101) of obtaining a phase map of the sample surface 6 by determining the phase of light reflected on the sample surface 6 having associated wavelengths. For example, the phase map can be obtained using the white light interferometer 1 in Figure 1.

[0051] The same white light interferometer or a different device may be used in step (102) to obtain a pre-height map of the sample surface 6. The pre-height map gives a first approximation of the height of the sample surface 6. This method aims to improve the accuracy of the pre-height map.

[0052] The method further includes the step (103) of identifying a first region 21 and a second region 22 of the sample surface 6, the first region 21 and the second region 22 being separated by an edge 23. The edge 23 can divide the sample surface 6 into two separate regions, as shown in Figure 3.

[0053] The method further includes step 104 of selecting a first position 24 adjacent to an edge 23 in a first region 22 and a second position 25 adjacent to an edge 23 in a second region 22, wherein the first position 24 is on the opposite side of the second position 25. As shown in Figure 3, the first position 24 and the second position 25 are separated by an edge 23. The edge 23 lies between the first region 24 and the second region 25, which would otherwise be adjacent. The first position 24 and the second position 25 shown in Figure 3 may be larger than the pixel size of the white light interferometer 1. In different embodiments, the sizes of the first position 24 and the second position 25 may be different.

[0054] The next step is to determine the pre-height difference between the first position 24 and the second position 25 based on a pre-height map (105), and to calculate the phase height difference between the first position 24 and the second position 25 based on a phase map and a specific wavelength.

[0055] The method includes the step (106) of determining the zero-phase edge height of the edge by calculating the difference between the pre-height difference and the phase height difference.

[0056] Following the step of determining the zero-phase edge height (106), the method includes the step of determining the height correction by determining the difference between the zero-phase edge height and an integer multiple of half of a particular wavelength (107).

[0057] Then, the height map is determined by correcting the heights of the first region 21 and the second region 22 in the pre-height map using height correction (108).

Claims

1. A method for determining a height map of a sample surface including edges, A step of obtaining a phase map of the sample surface by determining the phase of light reflected on the sample surface having a specific wavelength, The steps include obtaining a pre-height map of the sample surface, A step of identifying a first region and a second region of the sample surface, wherein the first region and the second region are separated by the edge, A step of selecting a first position adjacent to the edge in the first region and a second position adjacent to the edge in the second region, wherein the first position is on the opposite side of the second position, The steps include determining the prior height difference between the first position and the second position based on the prior height map, and calculating the phase height difference between the first position and the second position based on the phase map and the specific wavelength, The steps include determining the zero-phase edge height of the edge by calculating the difference between the pre-height difference and the phase height difference, The steps include determining the height correction by determining the difference between the zero-phase edge height and an integer multiple of half of the specific wavelength, The steps include determining a height map by correcting the relative heights in the first region and the second region in the pre-prepared height map using the height correction, A method of having.

2. The phase height difference is ΔH φ teeth, ΔH φ = Δφ λ / 4π Determined by, where Δφ is the phase difference between the first position and the second position, and λ is the specific wavelength. The method according to claim 1.

3. The aforementioned phase map is a wrap phase map. A method according to one or more of the prior claims.

4. An interferometer system, such as a white light interferometer system, is used, the pre-height map is obtained using the interferometer system, and the phase map is obtained using the interferometer system. A method according to one or more of the prior claims.

5. The step of identifying the first region and the second region is: The steps include obtaining an intensity map of the sample surface based on the intensity of light reflected from the sample surface, Optionally, the step of removing the background from the intensity map, The steps include identifying the edge based on the fact that the intensity of a pixel in the intensity map differs from the intensity of surrounding pixels, for example, based on the fact that the intensity of the pixel falls below a predetermined threshold, The steps include identifying the first region and the second region on both sides of the edge, Having, A method according to one or more of the prior claims.

6. The pre-height map is acquired based on the phase map and the specific wavelength. A method according to one or more of the prior claims.

7. The step of obtaining the aforementioned phase map is: A step of obtaining a group of interference fringe images by vertical scanning the sample surface through the focal plane of an interferometer system, wherein each interference fringe image includes the light intensity measured for each pixel of the interferometer system at each height of the sample surface relative to the focal plane, The steps include determining the covariance matrix for the aforementioned interference fringe image set, The steps include determining the principal components of the interference fringe image group by performing singular value decomposition of the aforementioned covariance matrix, The steps include selecting a first principal component related to the largest eigenvalue of the covariance matrix and a second principal component related to the second largest eigenvalue of the covariance matrix, A step of determining the measured phase for each of a plurality of pixels, based on the ratio of the vector component of the first principal component and the vector component of the second principal component, for example, by taking the arctangent, wherein each vector component is associated with each pixel. The steps include determining the phase map based on the phase measured for each pixel, Having, A method according to one or more of the prior claims.

8. An interferometer system for determining a height map of a sample surface including edges, the interferometer system comprising a light source, an optical sensor, and a processor, The aforementioned processor, The steps include obtaining a phase map of the sample surface based on the measurement of light having a specific wavelength reflected from the sample surface using an optical sensor, The steps include obtaining a pre-height map of the sample surface based on the measurement of the optical sensor of the light reflected from the sample surface, A step of identifying a first region and a second region of the sample surface, wherein the first region and the second region are separated by the edge, A step of selecting a first position adjacent to an edge in the first region and a second position adjacent to an edge in the second region, wherein the first position is on the opposite side of the second position. A step of determining a prior height difference between a first position and a second position based on the prior height map, comprising the step of calculating a phase height difference between the first position and the second position based on the phase map and the specific wavelength, The steps include determining the zero-phase edge height of the edge by calculating the difference between the pre-height difference and the phase height difference, The steps include determining the height correction by determining the difference between the zero-phase edge height and an integer multiple of half of the specific wavelength, The steps include determining the height map by the height correction of the heights of the first region and the second region in the pre-prepared height map, An interferometer system configured to perform the following actions.

9. The aforementioned processor, ΔH φ = Δφ λ / 4π By using the phase height difference ΔH φ It is configured to determine the following, where Δφ is the phase difference between the first position and the second position, and λ is the specific wavelength. The interferometer system according to claim 8.

10. The aforementioned phase map is a wrap phase map. An interferometer system according to any one of claims 8 to 9.

11. The interferometer system is a white light interferometer system equipped with a broadband light source, and the pre-height map is obtained using white light interferometry. An interferometer system according to any one of claims 8 to 10.

12. The aforementioned processor, The steps include obtaining an intensity map of the sample surface based on the intensity of light reflected from the sample surface, Optionally, the step of removing the background from the intensity map, Steps include identifying the edge based on the intensity of a pixel in the intensity map that falls below a predetermined threshold, Steps include identifying the first region and the second region on both sides of the edge, The system is configured to identify the first region and the second region by performing the following: An interferometer system according to any one of claims 8 to 11.

13. The processor determines the pre-height map based on the phase map and the specific wavelength. The interferometer system according to claims 8 to 12.

14. The aforementioned processor, For example, a step of acquiring a group of interference fringe images by moving an optical sensor relative to the sample surface, thereby causing the optical sensor to scan the sample surface perpendicularly through the focal plane of the optical sensor, wherein each interference fringe image includes the light intensity measured for each pixel of the interferometer system at each height of the sample surface relative to the focal plane, The steps include determining the covariance matrix for the aforementioned interference fringe image set, The steps include determining the principal components of the interference fringe image group by performing singular value decomposition of the covariance matrix, The steps include selecting a first principal component related to the largest eigenvalue of the covariance matrix and a second principal component related to the second largest eigenvalue of the covariance matrix, A step of determining the measured phase for each of a plurality of pixels, based on the ratio of the vector component of the first principal component and the vector component of the second principal component, for example, by taking the arctangent, wherein each vector component is associated with each pixel. The steps include determining the phase map based on the phase measured for each pixel, The system is configured to obtain the phase map by executing the following: An interferometer system according to any one of claims 8 to 13.

15. A computer-readable data storage medium comprising a computer program, which, when executed on the processor of an interferometer system according to one or more of claims 8 to 14, causes the interferometer system to perform the method according to any one of claims 1 to 7.

Images